code: def _legacy_default_index(format):
      if format._name == "FFMPEG":
          index = Ellipsis
      elif format._name == "GIF-PIL":
          index = Ellipsis
      else:
          index = 0
  
      return index
  
file_path: imageio/imageio/core/legacy_plugin_wrapper.py
imports: from pathlib import Path
  import numpy
  from ..config import known_extensions
  from .request import InitializationError, IOMode
  from .v3_plugin_api import ImageProperties, PluginV3
label_desc: Use image node_id 1 for calling a global function with example usage: _legacy_default_index(format) and returns: index